There has been a lot of reaction in the blogoshpere concerning our latest report called “5 Key Design Trends“. That’s fun, we like the discussion to continue and evolve. Below I’m posting a few of them. Check them out, they are all an interesting read.

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I recently got a query from one of the editors of Mother Earth News regarding a news story she had read in the New York Times. The writer, David Pogue, had been a judge in a contest sponsored by by the History Channel and the National Inventors Hall of Fame titled "Modern Marvels/Invent Now." A $25,000 prize was awarded to one amoung 25,000 contestants, and the winner was the Enertia House, which was invented by engineer and former log-home architect, Michael Sykes.

The Mother Earth News editor said that these homes had been featured in their magazine before. They essentially provide two wooden shells for the home, one inside the other. She said that there was no mention in the article about the cost per square foot. She was wondering what I thought about the concept from the standpoint of sustainable architecture.

Here is my response:

Double envelope house designs have been around for several decades and they definitely offer some benefits, as well as raise some questions. Any house that takes advantage of the geothermal properties of the ground will be doing its inhabitants and the earth a good turn. This can take the form of earth-sheltering in general, or some clever system of circulating air like the Enertia concept; coupled with sensible passive solar design, it is possible to approach a "zero energy" home.

The concerns about their system that I have are: The use of wood as the primary building material is not generally sustainable in this day of lost forests. With the double envelope design, you are practically building two houses to end up with one. Relying on wood as a thermal mass material compromises the potential thermal performance because wood does not serve this function nearly as well as traditional masonry thermal mass materials. So, I guess what I am saying is that a more sustainable and less costly design can be accomplished in more traditional ways.

Answering the same question, Paul Scheckel wrote, "At first glance, this looks a lot like sunspace design from the 70s (without the stone-filled basement to store heat) which overheated in the daytime and lost lots of heat at night. Consider also that this giant convection oven requires a temperature difference, which in this case is driven by the sun and the cool basement. A New England winter has precious little sun, so my heating system will drive the convective loop, increasing heat loss (in addition to the insulation-free envelope). I haven't heard too many people (ie: none) say that wood is bad for houses and better for biodiesel, but there are good arguments for not using so much material in a home. Does it work? I'd like to see one built in the northeast and see the resulting energy data, wherein the proof will lie."

Clark Snell of www.thinkgreenbuilding.com wrote, "I spent five minutes looking over the web site, so these comments are only based at looking at marketing materials, i.e. they may be inaccurate. Ditto what has been said so far. A couple more “red flags:”

1. Solid wood envelope. They seem to be using the old “mass enhanced R-value” argument for why solid wood walls perform well thermally. I think it’s well established that this is true only in very specific climatic situations. Touting solid southern yellow pine walls in comparison to solid white pine walls is like saying a Chevy Suburban gets better gas mileage than a Hummer…that’s not really a useful statistic.
2. Energy without oil. The presentation intimates that this is a completely passive design. For example, no heating system is mentioned. That simply isn’t credible for most climates using the technology they are describing.
3. Passive means local. You simply can’t create a design that relies heavily on passive techniques and generalize it across climates. In my area where we have high humidity, I’d wonder about this convective loop through the attic and basement, for example.

I could go on. I’m a passive design freak, so I’m all for the basic concepts they are dealing with. However, I don’t see anything really new here, but see marketing claims touting what they are doing as a major breakthrough and “the answer”. That always makes me nervous."

David Eisenberg, of www.dcat.net wrote, "After a skimming around their website, I see that they sell kits and their base prices don't include a lot of things - some of which are enumerated:

The idea of making walls by stacking bags of sand or earth has been around for at least a century. Originally sand bags were used for flood control and military bunkers because they are easy to transport to where they need to be used, fast to assemble, inexpensive, and effective at their task of warding off both water and bullets.

At first natural materials such as burlap were used to manufacture the bags; more recently woven polypropylene has become the preferred material because of its superior strength. The burlap will actually last a bit longer if subjected to sunlight, but it will eventually rot if left damp, whereas polypropylene is unaffected by moisture.

Because of this history of military and flood control, the use of sandbags has generally been associated with the construction of temporary structures or barriers. Using sandbags to actually build houses or permanent structures has been a relatively recent innovation.

It was an Iranian-born architect named Nader Khalili who has popularized the notion of building permanent structures with bags filled with earthen materials. Actually his first concept was to fill the bags with moon dust! Attending a 1984 NASA symposium for brainstorming ways to build shelters on the moon, Khalili coupled the old sandbag idea with the ancient adobe dome and arch construction methods from his homeland in the Middle East. He realized that bags filled with lunar “dirt” could be stacked into domes or vaults to provide shelter.

Khalili came up with a further refinement on this building concept on Earth: for a more permanent, shock-resistant structure, why not place strands of barbed wire between the courses of bags, thus unifying the shell into a more monolithic structure?

At first Khalili was filling his experimental bags with desert sand, but then he evolved his idea of “superadobe,” where bags or long tubes of polypropylene bag material would be filled with a moistened adobe soil that would dry into large adobe blocks. In this case the original bag material was merely the initial form and would not necessarily be an integral part of the eventual structure.

Soon after these first experiments, Khalili began publicizing his work through newspaper and magazine articles and conducting workshops and seminars on the techniques that he was perfecting. Many people who read about his work, visited his compound in Hesperia, California, or studied with him there, decided to go ahead with their own experiments with his ideas.

Among these “early adopters” were Joe Kennedy, Paulina Wojciechowska, Kaki Hunter and Doni Kiffmeyer, Akio Inoue, and Kelly Hart. I believe that it was Joe Kennedy who coined the more general term “earthbag” to suggest that the bag could contain a variety of earthen materials.

Paulina Wojciechowska was the first to write an entire book on the topic of earthbag building: Building with Earth: A Guide to Flexible-Form Earthbag Construction was published in 2001. This featured some of her early experiments done at Khalili’s CalEarth, along with several other case histories.

Akio Inoue, from Tenri University in Japan, has done extensive experimentation with earthbag construction, both on the campus of the University and in India and Africa where many other domes have been built for assistance programs.

Kaki Hunter and Doni Kiffmeyer (a couple) became enamored with earthbag construction after studying with Khalili, and worked on a variety of projects, both for themselves and for clients. In 2004 they wrote and got published another book, Earthbag Building: the Tools, Tricks and Techniques, based on their particular experience.

Kelly Hart (the author of this article) first began experimenting with earthbag building in 1997, after being exposed to the concept while producing his video program, A Sampler of Alternative Homes: Approaching Sustainable Architecture. He later documented his experience in actually building his own home in another program titled Building with Bags: How We Made Our Experimental Earthbag/Papercrete Home. Both of these programs are now available as DVD’s.

In the meantime, Nader Khalili was continuing the promotion of his “Superadobe” technique and eventually decided to patent the idea, which he obtained in the U. S. in 1999, using very general terms that cover using bags made of any material being filled with virtually any material, and combining these with barbed wired between the courses. While having made many public statements that this concept was his gift to humanity, he obviously wanted to capitalize on the potential economic reward.

Many of us who had been engaged in promoting earthbag building on our own were contacted by Khalili and asked to enter into contracts with him in order to continue our work. It didn’t take much research to discover that his patent could easily be disqualified because he had been publicizing his techniques through various media for at least four years before he even applied for his patent. Patent law clearly states that such publicity occurring prior to one year before the patent application would disqualify it for consideration.

So now the door is wide open for anyone to take this concept and run with it, and more people are doing so all the time, all over the world. While Khalili (and most of his students) have focused primarily on using the bags to form large adobe blocks, others have tried filling the bags with a variety of other materials, such as crushed volcanic rock, crushed coral, non-adobe soils, gravel, and rice hulls.

Earthbag building is unique among all other building technologies in that it can be either insulation or thermal mass, depending on what the bags are filled with. This is a very important distinction, because these characteristics of a wall greatly influence how comfortable, economical, and ecological any given system will be.

Safety is of prime concern with all building technologies, and much experimentation and testing has been done to establish guidelines for many ways of building. Khalili has established a relationship with the building department in Hesperia, California where CalEarth is located, an area where earthquakes are naturally a great danger. In 1993 live-load tests to simulate seismic, snow and wind loads were performed on a number of domed earthbag structures at CalEarth and these exceeded code requirements by 200%.

In 1995 dynamic and static load tests were performed on several prototypes for a planned Hesperia Museum and Nature Center to be constructed using Khalili’s Superadobe concepts with both dome and vault shapes. All of these tests exceeded ICBO and City of Hesperia requirements.

In 2006, at the request of Dr. Owen Geiger of the Geiger Research Institute of Sustainable Building, the Department of Civil and Mechanical Engineering of the U.S. Military Academy at West Point conducted several controlled and computer-monitored tests to determine the ability of polypropylene earthbags filled with sand, local soil, and rubble to withstand vertical loads. Their written report concluded that “overall, the earthbags show promise as a low cost building alternative. Very cheap, and easy to construct, they have proven durable under loads that will be seen in a single story residential home. More testing should prove the reliability and usefulness of earthbags.”

Despite the success of these tests, earthbag building concepts have yet to be incorporated into the International Residential Building Code. Obviously more enlightened acceptance of the demonstrated viability of earthbag building needs to occur!

It is difficult to know how many residences and other earthbag structures have been made at this point, probably hundreds if not thousands. Many of us have been promoting the technique for use as emergency shelters, and certainly some have been built for this reason. It is easy for folks to accept this way of building temporary shelters because it fits the historical model of sandbag use.

But many of us have also built substantial homes using earthbags, and in the process realized how truly versatile and sustainable the technique is. I wouldn’t be surprised if many of these earthbag homes are still standing long after their conventional counterparts built contemporaneously have disintegrated.

Today is Blog Action Day, a single day for all bloggers to post about one important issue, the environment. Most people think that Future House Now is a green site. It isn't. My primary focus is interesting modern homes, particularly those that are in the realm of realistic affordability for real families. But having said that, I frequently post about "green homes," and today is a good day to clarify my views on the subject.

First of all, why do I often post about green homes, even when my site is not purely focused on green issues? Well, for starters, green makes a lot of practical sense. It's laughable how much emphasis we put on greening our cars when we spend way more energy in our houses. It should be obvious every week when we take out the trash that our homes are the epicenter of our consumption habits. And I care about my family's health. I want them to live in a safe household environment, not one that is riddled with toxins and allergens.

Second, green isn't that hard to do anymore. You don't have to live in an Earthship made of tires pounded full of dirt, and old aluminum cans to be green (though that's pretty cool if you ask me). You also don't have to be an eco-warrior living off the grid in Northern California, growing all your own food and living off $10,000 worth of yearly organic produce sales. I guess what I mean is that being "green" isn't really an extreme lifestyle choice, it's part of everyday life for everyday people all over the USA. We have to stop treating green as extreme. Frankly, I think that alienates more people than it attracts. That's why I try not to overplay my green views, just as I don't downplay them either. To me, the important thing is that we're all constantly raising our awareness and incorporating green practices in our lives one little step at a time.

There are so many good ways to green any home, any style, old or new, anywhere. How about more efficient appliances, compact fluorescent light bulbs, better insulation, and low-VOC paints? These are pretty easy things that can make a big difference. How about not using those toxic cleaners in your kitchen and bathroom? Use good ol' white vinegar - it works great and is non-toxic. Inexpensive too. And great technology is here, with real strides in renewable energy being made every day. The reasons for not taking advantage of better technology for greener homes are becoming fewer and fewer. We're pretty much at the point where going green isn't about making tough choices, it's about making smart choices. The difference now isn't as much about toughness as it is about awareness.

I like to show interesting modern homes, and some of them are not particularly green. But lots of them are, in lots of different ways. Some are green just because they are compact. Some are green because they have a broad sheltering roof and good insulation. Some are green becaues they make good use of recycled materials, or new materials like steel framing that will last a long, long time without a lot of costly maintenance, and that can be recycled someday if need be. Maybe they aren't all perfect, but we can learn something from them. My site is about ideas. Some of the good ideas I like to show are about environmentally friendly homes, and some of the ideas are about other things. They're not mutually exclusive. And we have to stop thinking in those terms. Green fits with modern because they are both about good design. Good design has logic, economy and beauty all rolled into one. I see green as a part of that, not a whole unto itself.

Don't get me wrong, I don't take green for granted. I accept green as a matter of fact. That's how it should be - a natural part of life, not a radical philosophy. I view the recent mainstreaming of green as a sign that we've finally turned the corner. It won't be long now before we build the momentum to make lasting positive change. The challenges are real, but humanity, in spite of itself, is a problem solving species. We can do it.

Considering the fact that the average person produces 4.5 pounds of waste per day according to the EPA, we would be remiss not to address the question of household waste in our exploration of what it takes to make a green home. Thanks to more widespread public and private recycling programs and increased consumer awareness, Americans are definitely learning to tighten their ‘waste-line,’ but we still produce a phenomenal amount of garbage on a daily basis. Before we can talk about reducing, re-using and re-cycling, Green Home 101 needs to talk trash.

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Concrete "Firebowl" - $4,200.00 CAD with fire

An idea whose time seems to have arrived is the use of stockpiled shipping containers as modular units for building homes. Because of the balance of trade in the United States, these hefty steel boxes are piling up in ports around the country and posing a storage problem. Several architects and builders are taking advantage of this surplus to recycle the containers.

According to David Cross of www.sgblocks.com, "a container has 8000 lbs of steel which takes 8000 kwh of energy to melt down and make new beams etc... Our process of modifying that entire 8000 lbs of steel into a "higher and better use" only takes 400 kwh of electrical energy (or 5%). Granted it takes a bit more "muscle" but we call this Value-Cycling which we feel is that next step up from Re-cycling."

Each container measures 8 feet wide by 40 feet long by 9 feet tall. SG Blocks sells the finished structural systems (also called SG Blocks) for $9,000 to $11,000 per unit. The finished units have one or two walls removed and include the necessary support columns and beam enhancements.

According to KPFF Consulting, a structural engineering firm in St. Louis with extensive experience working with shipping containers, the units are stronger than conventional house framing because of their resistance to "lateral loads" -- those seen in hurricanes and earthquakes -- and because steel is basically welded to steel. The roof is strong enough to support the extra weight of a green roof — which has vegetation growing on it — if the owner should want it.

As for their energy efficiency, they claim that when the appropriate coatings are installed, the envelope reflects about 95 percent of outside radiation, resists the loss of interior heat, provides an excellent air infiltration barrier and does not allow water to migrate in.

One idea that has occurred to me is that this system might benefit from the use of SIP's (Structural Insulated Panels) for the roofs, rather that standard truss framing. SIP's are very well insulated, install quickly, and use much less wood than convention roofs.

Shipping containers are self-supporting with beams and stout, marine-grade plywood flooring already in place, thereby eliminating time and labor during the home-building process. Cross said construction costs are comparable to those in conventional building. Four to seven units are used in a typical home, he said.

Instead of nailing the siding they use "Super Therm", a ceramic paint made by Superior Products of Minnesota; it can be used as a paint, an adhesive, an insulator, a fireproofing material and an acoustic barrier. With this ceramic paint, they claim the insulation capacity is equal to a conventional house.

Adam Kalkin, of www.architectureandhygiene.com , has also become enamored with shipping containers as an architectural solution. The idea to do something with shipping containers came to Kalkin, a New Jersey resident, when driving to New York City, where he saw sky-high stacks of the unused cargo containers in the shipyards he passed.

"The cargo containers, with a life span of about 20 years when used for their original purpose, have an “infinite life span” when stationary and properly maintained," Kalkin says. “To me they are like a treasured antique: they may not be inherently valuable, but the history and the storytelling add value.”

Environmentalists have embraced the design, applauding the recycling inherent to Kalkin's designs. And advocates for affordable-housing like the design, since according to Kalkin, "the total cost of a house—between $150,000 and $175,000 after the buyer settles upon the various options—works out to be between $73 and $90 per square foot, about half the cost of the conventional $200 per square foot for reasonable quality, new construction in the Northeast.”

Kalkin has recently opened a factory—“a hangar at a little airport in New Jersey”—to manufacture Quik Houses. “There are a lot of elbows flying in this process, and this is the best way to protect the quality of the house, to keep the accounting transparent, and to make sure I am not unwittingly responsible for heinous crimes to the built environment.” Once the factory is fully functional, Kalkin plans to export many of his products, commenting that “the possibilities of working on a world scale are exciting.”

Twenty-one thousand containers hit American shores every day of the year. Containers can be shipped to the interior of the country via trains and trucks. Shipping containers are like Lego toys and the modules can be assembled in thousands of ways.

In general it is a good thing to recycle materials that otherwise have no further use for their intended purpose, and this is true here. As for whether one can make a comfortable house out of these metal boxes, the biggest question is: insulation...it is essential, but there are many ways to insulate these containers, so this is not a big concern. Another concern that many people would have is whether a metal box would have adverse health effects because of EMF (electro-magnetic frequencies) generation or propagation. Some people are sensitive to these while others are not.

There is no doubt that these containers can be used to fabricate very strong shells that would withstand substantial abuse from the ravages of nature.

There is a manufactured building system that has been gaining popularity in Europe for several years called Thermoplan or Zeigel Blocks. While I have no personal experience with this technology, I can readily see its many advantages. As far as I know this system has not made its way across the ocean to North America. From what I can gather from the websites (referenced below), here are some of the advantages:

Thermoplan or Zeigel Blocks are fired clay blocks which use about 1/3 less energy to make compared to concrete blocks, and about 2/3 less CO2. They are fast, simple and ideal for a self builder to use. About 50% of German homes are made this way and the technology is spreading to other areas of Europe.

Thermoplan systems use Ziegel blocks with a thin bed of mortar, to provide a breathing wall construction system. When combined with woodfibre board they can form a thermally and acoustically high performance shell. The Ziegel blocks come as part of a full load-bearing external and internal wall masonry system, and combine high thermal performance with robustness, speed of build and a breathing wall design.

Because of all the trapped air and the thickness of the walls, these blocks provide reasonable insulation, while at the same time do provide some degree of interior thermal mass for maintaining constant interior temperatures. This is an unusual combination of these two factors in a single wall system.

See www.burdensenvironmental.com or www.natural-building.co.uk for information for this innovative system.

Strawboard building panels are a kind of structural insulated panel (SIP) designed to replace 2x4 stud and drywall construction for both interior and exterior walls, as well as provide load and non-bearing ceilings, roofing, doors, flooring, and prefabricated buildings. These environmental friendly, solid panels are made of all natural fibrous raw materials, mainly wheat and rice straw. The durable panels feature thermal and acoustic insulation as well as fire and termite resistance and are available for a variety of applications to speed up the construction processes. While these have been used in over 20 countries for more than 50 years, strawboard panels have only been introduced to the U.S. in the past few years.

Strawboard panels have a solid core of compressed wheat or rice straw. High pressure and temperatures forces the straw to release a natural resin that binds the fibers together. The compressed panels are then covered with either paper liners or OSB that is adhered to both sides with water based non-toxic glue. The standard panel measures 4 feet by 8 feet by 2-1/4 inches to 8 inches, weighing from 140 lbs. to 440 lbs. each. Custom panel sizes are available ranging from 3 feet to 12 feet long.

The panel's high density and low oxygen content does not support combustion. Since the panels do not contain added resins, alcohol, or other chemicals, no flammable vapors are produced. The panels have an R-value of between 3 and 25, depending on the composition and thickness. For permanent protection against insects and fungal decay and additional fire resistance, the boron compound polybor can be factory added to the core.

The product's workability is similar to wood as it can be sawn, drilled, routed, nailed, screwed, and glued. Lightweight wall attachments such as shelf brackets, picture frames, mirrors, and towel bars can be attached directly to the panel.

Since straw is a renewable by-product of wheat and rice production that becomes available annually, it takes less acreage (by about half) to build an equivalent house than with standard lumber, and which would then potentially preserve that forest for ecological habitat and CO2 sequestration.

See www.stramit-int.com/ for panels available in Europe and www.agriboard.com for panels available in the U.S.

I received an email from Professor Sunny Cai, who teaches architectural design at a college in Beijing , China. He mentioned his interest in ancient Chinese architecture, especially the earthen buildings called “tulou,” and he sent me some pictures of these rammed earth buildings.

I had never seen anything quite like them, so I queried him further about how they were made and used. He replied, “The foundation was built with rocks, 2 feet high all around. The juice of glutinous rice and some lime is mixed into the earth for strength, and then sliced bamboo, reeds, and sometimes pieces of wood are also used.”

This picture was taken in front of a rammed earth building with Sunny Cai and his students.

I did some further internet research and found out more about these interesting structures. Tulou are traditional communal residences in the Fujian province of Southern China, often of a circular configuration surrounding a central shrine. Some of these vernacular structures were constructed of cut granite or had substantial walls of fired brick. The end result is a well lit, well-ventilated, windproof, earthquake resistant building that is warm in winter and cool in summer.

There are more than 20,000 tulou in southern Fujian, and these were designated as a UNESCO World Heritage site in 2008 as “exceptional examples of a building tradition and function exemplifying a particular type of communal living and defensive organization, and, in terms of their harmonious relationship with their environment".

Actually the Tulou were built by a minority called the Hakka, who were originally Han who fled south to escape war and famine during the Qin Dynasty (221-206 BC). As they gradually moved they changed the local architecture by incorporating Han styles and that produced the tulou. Not only were the high walls built for defense but they were also the result of traditional Han architecture. Tulou were mostly built between the 12th to the 20th centuries. The oldest one was constructed over 1,200 years ago and is regarded as a “living fossil” of the construction style of central China.

There are three types of Tulou. The Wufeng has three halls and two side rooms and are said to be the result of a redesign of the Han courtyard. The oldest tulou are the rectangle ones, and the most emblematic ones are round. They are typically designed for defensive purposes and consist of one entrance and no windows at ground level. The biggest round one can have up to five stories with three interior rings. The largest houses cover over 40,000 m² and it is not unusual to find surviving houses of over 10,000 m². Most round tulous are three or four stories, with family kitchens and livestock on the ground floor. The next floor becomes a storage room for food and furniture (with no windows), and above that are the bedrooms.

These structures are exemplary of sustainable architecture in that they are built of local, natural materials with simple techniques. They have good thermal attributes, with the massive earthen walls to help buffer temperatures. They are obviously built to last, and house many of the necessities for life. And they embody a communal life style that conserves energy and resources; these represent a form of ancient co-housing.

Each year the Society for Environmental Graphic Design sponsors a contest to recognize the best in environmental graphic design. This year’s Juror’s Award went to Norman Lee and Charles Houser for their Billboard Earthbag Project.

The designers say: “Because most conventional sandbags are fabricated from polypropylene, they are very vulnerable to UV rays and quickly begin to deteriorate when exposed to the sun. Consequently, earthbag shelters need to be plastered to maintain their durability during extended use.The Billboard Earthbag Project envisions using billboard vinyl as an alternative material for earthbags. Polyvinylchloride (PVC) or vinyl, a virtually indestructible, UV-resistant material that cannot be incinerated because of the toxic gases it would emit, represents a substantial portion of the PVC in the world’s overburdened landfills. Because of its durability and imperviousness to the sun and other elements, billboard PVC is an ideal material for reuse.”

“The reuse of billboard vinyl in earthbag construction mitigates the impact of global warming in two ways. Transforming this landfill-bound material into another useful product helps lessen landfill overflow worldwide. It also eliminates the need to protect earthbags from UV rays, resulting in more robust emergency shelters that can be used longer to lessen the human suffering caused by natural disasters.”

“As a visual concept, each billboard shelter stands as a symbolic gesture of sustainability. Beyond its environmental benefits, the strategy of reusing billboard vinyl visually recontextualizes the nature of billboards, which are symbols of mass consumerism and a pervasive form of visual pollution in our world. This concept does not seek to generate imagery, but instead appropriates existing commercial imagery as a metaphor for global recycling and reuse. Assembled together into a shelter, the earthbags create a dynamic and vibrant pattern of collaged images and text from around the world, dramatically suggesting a unified, international gesture of sustainability, hope, and humanitarianism.”

According to the jurors, they "were intrigued by this project as an example of ‘cradle-to-cradle’ design pertinent to the signage industry. Utilizing intrinsic qualities of billboard PVC—UV resistant and near indestructible—this concept proposes the creation of dwellings from recycled material and imagery. The idea takes the recycling of billboards, street banners, and print graphics—already employed by art museums in the creation of second-use products—to another level. Truly inventive!"

This all sounds pretty good, and might well work if the billboard material were cut and sewn into bags. One obvious disadvantage of the idea is that since PVC is toxic when burned, this would present a potential hazard to the occupants, but of course this is true of many modern building materials. PVC poses a great risk in building fires, as it releases deadly gases long before it ignites, such as hydrogen chloride which turns to hydrochloric acid when inhaled. As it burns it releases yet more toxic dioxins. Additionally, vinyl does outgas highly toxic VOCs over time. Fortunately most of this danger would have passed with the use of recycled signs, but this could also be an issue.

Dr. Owen Geiger and I have just found that a book published in 1990 in Germany, Building with Pumice, written by Klaus Grasser and Gernot Minke, describes experiments done in the 1970’s at the Research Laboratory for Experimental Building at Kassel Polytechnic College in Germany that have considerable bearing on the history of earthbag building.

Most of the book is about the physical properties of pumice, how to obtain and process it, and how to make blocks or walls with pumice/cement, but the fifth and final chapter, titled “Building with Unbonded Pumice,” describes how they began to investigate the question of how natural building materials like sand and gravel could be used for building houses without the necessity of using binders. The use of fabric-packed bulk material was found to be a cost-efficient approach. They used pumice to pack in the bags, because it weighs less and has better thermal insulating properties than ordinary sand and gravel. Their first successful experiments were with corbeled dome shapes (an inverted catenary) which was obtained with the aid of a rotating vertical template mounted at the center of the structure.

1978, a prototype house using an earthquake-proof stacked-bag type of construction was built in Guatemala. They used cotton bags soaked in lime-wash to protect the material from rot and insects. When flattened, the bags measured roughly 8 X 10 cm. Vertical bamboo poles placed on both sides of the bags and interconnected with wire loops gave the stacked bags stability. The bamboo rods were fixed to the foundation and to the horizontal tie beam at the top.

Obviously the concept of constructing homes with fabric bags of mineral material predates Nader Khalili’s earliest experiments by many years, and I was certainly not the first to experiment with filling earthbags with pumice! The entire chapter is reproduced as an article at www.greenhomebuilding.com.